Sex-biased parental care and sexual size dimorphism in a provisioning arthropod

Field, Jeremy; Shreeves, Gavin; Kennedy, Martyn; Brace, Selina; Gilbert, James D. J.

Abstract

The diverse selection pressures driving the evolution of sexual size dimorphism (SSD) have long been debated. Whilst the balance between fecundity selection and sexual selection has received much attention, explanations based on sex-specific ecology have proven harder to test. In ectotherms, females are typically larger than males, and this is frequently thought to be because size constrains female fecundity more than it constrains male mating success. However, SSD could additionally reflect maternal care strategies. Under this hypothesis, females are relatively larger where reproduction requires greater maximum maternal effort—for example where mothers transport heavy provisions to the nests. To test this hypothesis, we focussed on digger wasps (Hymenoptera: Ammophilini), a relatively homogeneous group in which only females provision offspring. In some species, a single large prey item, up to ten times the mother’s weight, must be carried to each burrow on foot; other species provide many small prey, each flown individually to the nest. We found more pronounced female-biased SSD in species where females carry single, heavy prey. More generally, SSD was negatively correlated with the numbers of prey provided per offspring. Females provisioning multiple small items had longer wings and thoraxes, probably because smaller prey are carried in flight. Despite much theorising, few empirical studies have tested how sex-biased parental care can affect SSD. Our study reveals that such costs can be associated with the evolution of dimorphism, and this should be investigated in other clades where parental care costs differ between sexes and species.

Citation

Field, J., Shreeves, G., Kennedy, M., Brace, S., & Gilbert, J. D. J. (2015). Sex-biased parental care and sexual size dimorphism in a provisioning arthropod. Behavioral Ecology and Sociobiology, 69(12), 1897-1906. https://doi.org/10.1007/s00265-015-2002-1

• Acceptance Date: Sep 1, 2015
• Online Publication Date: Sep 14, 2015
• Publication Date: Dec 1, 2015
• Deposit Date: Mar 18, 2016
• Publicly Available Date: Mar 18, 2016
• Journal: Behavioral ecology and sociobiology
• Print ISSN: 0340-5443
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 69
• Issue: 12
• Pages: 1897-1906
• DOI: https://doi.org/10.1007/s00265-015-2002-1
• Keywords: Sexual dimorphism; Parental care; Hymenoptera; Wasps
• Public URL: https://hull-repository.worktribe.com/output/433829
• Publisher URL: http://link.springer.com/article/10.1007/s00265-015-2002-1
• Additional Information: This is the author's accepted manuscript of an article which has been published in: Behavioral ecology and sociobiology, 2015, v.69, issue 12. The final publication is available at Springer via http://dx.doi.org/10.1007/s00265-015-2002-1
• Contract Date: Mar 18, 2016